Tape tensioning device



United States Patent Iowa Filed June 29, 1964, Ser. No. 378,828 3 Claims. (Cl. 242-752) This invention rel-ates generally to tape tensioning devices and more particularly to a simplified tape tensioning device which provides an adjustable drag for a tape, such as magnetic tape, which is pulled through said device.

There are in the prior art many structures which function to provide a drag for a tape such as a magnetic tape. Many of these prior art devices employ two rollers which are spaced apart and over which the tape is caused to pass. The two rollers are constructed to rotate at different angular velocities so as to provide a slippage effect on the tape. Since the angular velocities of the two rollers are different there must be slippage between the tape and at least one of the rollers. Such slippage provides a drag on the tape so that some tension is produced between a capstan or take-up reel and the two rollers. It should be noted that in such prior art devices, the two rollers are spaced apart from each other so that the tape passes over each of the two rollers, but does not pass between the two rollers. In other words, the two rollers do not form a bite therebetween to grip the tape as it passes therebetween. In some prior art devices the mechanism for providing different angular velocities for the two rollers is relatively complex and, further, the amount of slippage is sometimes difficult to maintain at a constant value with the result that the drag on the tape is difficult to maintain at a constant value.

An object of the present invention is to provide a simplified structure for providing drag on a tape.

A further object of the invention is to provide an inexpensive and reliable structure for providing drag on a tape which drag remains relatively constant.

A third object of the invention is to provide a mechanism comprising two rollers which are geared together so as to have different angular velocities and which provide a bite on a tape passed therebetween to cause a drag on said tape.

A further object of the invention is the improvement of tape tensioning devices generally.

In accordance with the invention, there is provided a pair of rollers whose rolling surfaces contact each other and which have axes of rotation parallel with one another. The two rollers are geared together by a pair of gears having a gear ratio such that the circumferential velocities of the two rollers are necessarily different. A tape pulled between the .two rollers, which are springloaded against each other, cause the two rollers to rotate but at different circumferential velocities determined by the aforementioned gear ratio. This difference in circumferential velocity or surface speed of the rollers results in a drag on the tape as it passe-s between the rollers.

A feature of the invention lies in the fact that because the slippage velocity between the tape and the two rollers can be made small, the wear on the tape can be maintained at a minimum value.

Another feature of the invention is that no drive is required for either of the two rollers since the tape itself, as it passes between the two rollers, provides the necessary drive to the rollers; the different circumferential velocities of the two rollers providing the desired tape drag.

The above-mentioned .and other objects and features of the invention will be more fully understood from the following detailed description thereof when read in conjunc- 3,285,529 Patented Nov. 15, 1966 ice tion with the drawing, which shows a perspective view of the invention.

Referring now to the figure, there is shown a pair of rollers 12 and 18 which rotate, respectively, on shafts 11 and 22. At one end the shafts 11 and 22 rotate in plates 9, 10 with suitable bearings (not specifically shown). At the other ends the shafts 11 and 22 rotate respectively in the supporting surfaces 17 and 19, which are equipped with suitable bearing structures, again not specifically shown. The supports 9, 10, and 17, 19'are spring-loaded by tension springs 25 and 28 which hold the rollers 12 and 18 together with a predetermined force, determined by the tension of springs 28 and 25. Also mounted upon shafts 11 and 22 and designed to engage each other are the gears 13 and 14. Said gears 13 and 14 are fixed securely to the rollers 12 and 18, respectively, and will of course rotate therewith.

The gear ratio of the gears 13 and 14 is such that the circumferential velocity of the rollers 12 and 18 are different. More specifically, assume for purposes of discussion, that the diameter of rollers 12 and 18 are the same. Then, to cause the circumferential velocity of roller 12 to be less than that of roller 18, the gear 13 is constructed to have a larger diameter than gear 14 and, consequently, to have more teeth than gear 14.

The rollers 12 and 18 can be of any suitable material necessary to produce the desired drag on a given tape. For example, rollers 12 and 18 can be of metal, plastic, or a rubber compound.

In the operation of the structure, a tape 20 is pulled through rollers 12 and '18 in the direction of the arrow 23 by suitable means, such as a capstan (not shown) or a take-up reel 21. It is apparent that other rollers and capstans may be positioned between take-up reel 21 and the two rollers 12 and 18. However, for purposes of simplicity of explanation, they are omitted and only the take-up reel 21 is shown. The difference in angular velocity of the two rollers 12 and 18 produces a slippage between the surface of at least one of the rollers and the surf-ace of the tape 20 as the tape is pulled between the rollers. Such slippage and the drag produced thereby is determined by the force with which the two rollers are held together by springs 28 and 25, the difference in circumferential velocity of rollers 12 and 18, and the surface friction between the rollers 12 and 18 and the tape 20. By varying one or more of the above-mentioned factors, tape drag can be varied over a considerable range.

As will be apparent, some wear will be produced on the tape inasmuch as slippage is present. However, by proper design the wear on the tape can be kept at a minimum. One of the principal factors determining wear is the difference in circumferential velocity of rollers 12 and 18. By keeping such difference velocity small, the wear on the tape 20 can be kept small.

An alternative way of increasing the drag on the tape is to increase the tension of the spring 28 (rather than increasing the difference in circumferential velocity between rollers 12 and 18). Increasing the drag by means of adjusting the spring tension is quite effective and produces relatively little increase in tape wear. It is evident, however, that some difference in angular velocity is essential to provide drag on the tape.

Another factor entering into the determination of the amount of drag on the tape is the angle of wrap of the tape around either the roller 12 or 18. If, for example, the tape is wrapped around a substantial portion of roller 18, the roller 18 will tend to rotate at a circumferential velocity equal to the linear velocity of the tape 20 and the slippage will occur between the tape 20 and the roller 12. The roller 12 has a smaller circumferential velocity than the roller 18, thus providing the drag on the tape.

If the tape were wrapped around a substantial portion of the roller 12, then there would be no slippage between the roller 12 and the tape 20; the slippage occurring between the tape 20 and the roller 18. However, if no slippage occurs between the roller 12 and the tape 20, this would mean that the roller 18 which has a higher circumferential velocity than roller 12 would tend to push the tape out ahead of the two rollers 12 and 1-8 towards the take-up reel 21. Obviously, such a condition is unstable since the take-up reel would immediately take up any such slack. In actuality, there is some drag on the tape under such conditions since the tape itself tends to hold back the circumferential velocity of roller 18. Since roller 18 is geared to roller 12, the circumferential velocity of roller 12 tends to be retarded, thus producing a drag on the tape.

it is to be noted that the form of the invention shown and described herein is but a preferred embodiment thereof and that various changes may be made in the design thereof without departing from the spirit or the scope of the invention.

I claim: 1. Tape tensioning means comprising: first and second unpowered roller means positioned side by side with their axes of rotation parallel to one another, means for pressing the circumferential perimeters of said rollers together to grip a tape positioned there- 'between, coupling means constructed to maintain a (fixed ratio, other than unity, of the circumferential velocities of 4 said first and second rollers, when either of said rollers is caused to rotate by a tape being pulled therethrough,

and means for pulling said tape between said rollers.

2. Tape tensioning means in accordance with claim 2 in which:

the axes of said rollers each comprises shaft means,

supporting means for supporting said shaft means,

and .in which said coupling means comprises gear means secured on said shaft means of said rollers and having a gear tooth ratio to provide said fixed ratio of circumferential velocities.

3. Tape tensioning means in accordance with claim 2 in which said means -for pressing said rollers together comprises spring means constructed to force one of said rollers towards the other roller.

References Cited by the Examiner UNITED STATES PATENTS 1,539,754 5/ 1925 McC-ullougho 242-75.2 1,986,776 1/1935 Moore 24275.2 X 1,998,931 4/1935 Kellogg 226 X 2,057,553 10/ 19 36 B-oecking 226195 X 2,102,793 12/ 1937 George 24275.2 X 2,373,107 4/1945 Duffy 226-195 X FRANK J. COHEN, Primary Examiner. MERVIN STEIN, Examiner. N. L. MINTZ, Assistant Examiner. 

1. TAPE TENSIONING MEANS COMPRISING: FIRST AND SECOND UNPOWERED ROLLER MEANS POSITIONED SIDE BY SIDE WITH THEIR AXES OF ROTATION PARALLEL TO ONE ANOTHER, MEANS FOR PRESSING THE CIRCUMFERENTIAL PERIMETERS OF SAID ROLLERS TOGETHER TO GRIP A TAPE POSITIONED THEREBETWEEN, COUPLING MEANS CONSTRUCTED TO MAINTAIN A FIXED RATIO, OTHER THAN UNITY, OF THE CIRCUMFERENTIAL VELOCITIES OF SAID FIRST AND SECOND ROLLERS, WHEN EITHER OF SAID ROLLERS IS CAUSED TO ROTATE BY A TAPE BEING PULLED THERETHROUGH, AND MEANS FOR PULLING SAID TAPE BETWEEN SAID ROLLERS. 